Prostheses for implantation in blood vessels or other similar organs of the living body are, in general, well known in the medical art. For example, prosthetic vascular grafts constructed of biocompatible materials, such as DACRON material or expanded, porous polytetrafluoroethylene (ePTFE) tubing, have been employed to replace or bypass damaged or occluded natural blood vessels. A tubular graft material supported by framework is known as a stent-graft or an endoluminal/endovascular graft. In general, endovascularly delivered stent-grafts typically have framework that includes at least one graft anchoring component that operates to hold the tubular graft in its intended position within the blood vessel. Most commonly, the graft anchoring component is one or more radially compressible stents that are radially expanded in vivo to anchor the tubular graft to the wall of a blood vessel or anatomical conduit. Thus, endovascular grafts are typically held in place by mechanical engagement and friction due to the apposition forces provided by the expandable stents. In general, the use of stent-grafts for treatment or isolation of vascular aneurysms and vessel walls, which have been thinned or thickened by disease (endoluminal repair or exclusion), are well known.
In general, rather than performing an open surgical procedure to implant a graft that may be traumatic and invasive, endovascular grafts or stent-grafts are preferably deployed through a less invasive intraluminal delivery. These stent-grafts may include either self-expanding or balloon-expandable stent structures with a tubular graft component attached to the stent structure. The stent-graft can be reduced in diameter, by crimping onto a balloon catheter or by being contained within a sheath component of a delivery catheter, and advanced through the venous or arterial vasculature. More particularly, a lumen of the vasculature is accessed at a convenient and low trauma entry point, and the compressed or crimped stent-graft is routed through the vasculature to the site where the prosthesis is to be deployed. Once the stent-graft is positioned at a treatment site, the stent structure may be radially expanded or allowed to radially expand so that at least a portion of it contacts and substantially conforms to a portion of the surrounding interior wall of the lumen, e.g., the blood vessel wall or in another application an anatomical conduit, to hold the graft component firmly in place.
More particularly, intraluminal deployment of a self-expanding stent-graft is typically effected using a delivery catheter with coaxial inner (plunger) and outer tubular members arranged for relative axial movement. The stent-graft is compressed and disposed within a distal end of the outer tubular member in front of or distal to the inner tubular member. The delivery catheter is then maneuvered, typically routed though a lumen, e.g., vessel, until the distal end of the catheter with the stent-graft compressed therein is positioned at the intended treatment site. The inner tubular member is then held stationary to prevent proximal movement of the stent-graft while the outer tubular member of the delivery catheter is proximally withdrawn. As the outer tubular member is withdrawn, the stent-graft radially expands so that at least a portion comes into substantially conforming surface contact with a portion of the interior of the lumen, e.g., blood vessel wall.
Many current commercial and clinical stent-graft delivery systems employ a relatively stiff outer member, or catheter shaft, to restrain the stent or stent-graft during introduction and tracking to an intravascular treatment site. The stiffness of such a catheter shaft, when combined with a relatively stiff guidewire, may straighten the patient's anatomy and thus increase the chance of vessel trauma during the procedure. Some manufacturers have addressed the stiffness of these devices by incorporating a textile, or flexible, catheter segment within the delivery system. The more flexible catheter segments are conventionally contained inside the stiffer, outer catheter shaft, which is employed during introduction and tracking of the catheter to the anatomy in the vicinity of the intravascular treatment site. Once so positioned the stiffer outer catheter shaft is withdrawn to expose the underlying flexible catheter segment, which is then maneuvered and positioned within the treatment site and subsequently retracted, or otherwise removed from constraining the stent-graft. Delivery devices having the afore-mentioned configuration do not address the potential trauma caused by introduction and tracking of the catheter devices prior to exposure of the flexible catheter segment and require a two-step delivery process.
Thus, those of skill in the art seek improvements in providing an endovascular stent-graft delivery system that exhibits improved flexibility without the bulkiness and larger crossing profile of a double sheath delivery system, and that may be introduced and tracked through the vasculature with minimal trauma. Embodiments of a stent-graft delivery system are described herein that improve flexibility by incorporating a textile segment as a distal outer shaft portion of the delivery system to lessen the effects of introducing and tracking the delivery system to the desired intravascular treatment site.